Cable systems



E. J.` MERRELL July 12, 1955 CABLE SYSTEMS 2 Sheets-Sheet l Filed Aug.13. 1951 JNVENTOR. bw/N Aff/wia July 12, 1955 E. 1. MERRELL 2,713,081

, CABLE SYSTEMS Filed Aug. 13, 1951 2 Sheets-Sheet 2 1N V EN TOR. raw/,vd MEE/Pa L United States Patent Ehce Zifiti Patented duly 12, 1955 CABLESYSTEMS Edwin J. Merreli, Scarsdale, N. Y., assigner to Phelps DodgeCopper Products Corporation, New York, N. Y., a corporation of DelawareApplication August 13, 1951, Serial No. 241,556

1 Claim. (l. 174-14) This invention relates to an improvement in`electric cable systems of the type wherein one or more insulated cablesare loosely immersed in oil, or equivalent liquid insulating medium inpipe. v

In such systems the ends of the cables are enclosed in terminations orpotheads which also contain oil.

The oil in the pipe is not under electric stress and therefore amoderate amount of contamination is not of great importance. The oil inthe terminal is under electric stress and contamination would be liableto lead to terminal failure.

It is not practicable to merely seal the entry of the cable into thepothead in order to effect separation of the two oil systems becauseexpansion of the oil, both that in the pothead itself and that from thecable insulation, would result in excessive pressures in the potheadswhich, usually having porcelain walls, would be thereby endangered andfailures would likely occur.

The objects of the present invention are to equalize pressures in pipeand terminals, to prevent excessive pressures in the terminals, toensure the retention of oil in the terminals in the event of loss ofpressure in the pipes and to prevent contamination of the oil in theterminals by that in the pipe.

It is therefore necessary, not only to seal the entry of the cable intothe pothead by means of a stuing box, but also to provide a by-pass tothe seal to relieve the pressure. Means to accomplish this are wellknown, one being to provide a pair of valves in the by-pass, whichpermit the egress of oil from the pothead when the pressure reaches apredetermined value and the other to permit of entrance of oil to thepothead when the pressure in the latter drops\to a predetermined value.

This means has the disadvantage of permitting contaminated oil from thepipe oil system to enter the potheads. Another means provides a movablediaphragm in the by-pass which expands or contracts in accordance withthe pressure requirements of the pothead. These both have thedisadvantage of moving parts with im evitable wear and unpredictablelife.

The present invention, like the latter system, provides means forpressure equalization and prevention of oil contamination but does sowithout moving parts.

The means employed consists in the use of an oil filter in the by-pass.Such a device may be of the tilterpaper type or the adsorbent powdertype commonly used for oil lltration. Oil will pass through the iilteronly when there is a difference of pressure across it.

The foregoing and other features of my invention will now be describedin connection with the accompanying drawing forming part of thisspecification in which I have illustrated my cable system in itspreferred form, after which l shall point out in the claim thosefeatures which I believe to be new and of my own invention.

In the drawings:

Figure l is a sectional View of a cable terminal to which my inventionis attached.

Figure 2 is a section along the line 2--2, Figure 1.

Figure 3 is a modification shown in diagram which I may employ, adaptedto a three cable termination.

Figure 4 is a further modification showing a crosssection similar tothat shown in Figure l with a different iilter attachment.

In the carrying out of my invention, 16 is a pipe containing a cable 11,ending in a terminal 12. A stuffing box seal is shown at 13. A by-passis shown at 14 which for simplicity, is shown exterior to the terminal(see Figures l and 3) but which may be incorporated in the base of theterminal (see Figure 4). For purposes of illustration, a paper typefilter is shown at 15 within the by-pass 14.

In Figure l, l illustrate a paper type filter 15 which is shown in itssimplest form and comprises a paper filter element 16 held between twosupporting plates 17 and connected in the by-pass line 14.

In Figures 3 and 4 my lter element 16 is shown supported between twocapsules 18 and 19. These metal capsules or cylinders are perforated at20 and have closed ends 21 and the filter element 16 is packed inbetween the capsules.

With special reference to Figure 3, I show a diagrammatic sketch of athree cable termination in which the stuffing box element 13 is shown ineach cable termination a distance down from the pothead with the element13 in ali three lines by-passed through a single filter element 16. Myfilter element in this View is supported between two capsules i8 and 19.The by-pass line in each of the three cables passes through a singlefilter.

Referring especially to Figure 4: This is an enlarged detail of amountina which I may use in which 30 and 31 are structural mountingplates and in which the pipe l@ is securely fastened and held. A passaged@ (two are shown) extends through this mounting plate 30 and is adaptedto receive the filter element 16 at the upper end, the lower end isexposed to the space 41 which is open to the inside of the pipe line 10.It will be readily understood that with any differential of pressure theuid in the pipe 1l) will pass through the filter 16 and into terminal12. The fluid travels through space 41, passageway and filter element 16which is supported between the perforated plates 1S and 19. Anyimpurities of the insulating fluid in the pipe line will therefore bekept out of the fluid in the terminal and will thereby eliminateterminal failures.

In operation when high ambient temperature or heat from the conductorwithin the terminal or exudation of oil from the cable, or anycombination of these, causes a rise in pressure within the terminal, sothat the pressure is in excess of that in the pipe, oil will be forcedthrough the iilter element 16 and the pressure in the terminal relieved.lf, due to low ambient temperatures, drop of load or any combination ofthese or other causes, the pressure in the terminal should drop belowthat in the pipe, oil will be forced through the lter element 16 andwill restore the pressure in the terminal and, at the same time filterit, so that the oil that enters the terminal will be free of any impuriythat may have contaminated the pipe oil.

Due to the alternating llow of the oil through the filter, there will bea tendency for the filter to be selfcleansing. However, provision wouldbe made for the replacement of the ltering medium without loss ofpressure, such as by means of valves 46 and 47 in the by-pass pipes.

I wish it distinctly understood that my cable system herein describedand illustrated is in the form in which I desire to construct it andthat changes or variations may be made as may be desirable or convenientwithout departing from the salient features of my invention and Itherefore intend the following claims to cover References Cited in tl'ieflle of this patent UNITED STATES lPATENT-S Eby Nov. 3, 1931 Hochstadteret al. May 11, 1937 Whisler Oct. 19, 1937 Unger Apr. 25, 1950 Nelson May30, 1950

